Multiple Chip selects are used when there are multiple components sharing the same Bus (address , data or Both) the chip selects are used to decode or select one of the multiple components and deselect the others

Higher performance (read as frequency) products tend not to share Bus due to signal integrity limitations when extra loads are hanging on the Bus. These parts are typically used in Point to point connections as compared to the lower performance products where Multi-drop is OK. As a result, higher performance products tend to have fewer or no chip selects